After reclaiming leadership of the Democratic Party in Sunday's primary, in which he secured more than 70 per cent of votes nationwide, he tweeted: "It is a huge responsibility". That put him far ahead of Justice Minister Andrea Orlando with 20 percent and Michele Emiliano, the governor of the southern Puglia region, with about five percent.

Renzi, 42, resigned as prime minister in December after Italians overwhelmingly rejected a constitutional referendum aimed at streamlining the country's parliamentary system.

National elections are due in spring 2018, but Renzi, eager to regain the premiership, has been maneuvering for a possible early election. Renzi's ability to counter the 5-Star surge may be crucial to fending off an existential threat to the euro zone.

Italy's former prime minister Matteo Renzi received a fresh mandate as the secretary of center-left Democratic Party (PD) after a PD primary election held on Sunday.

The PD-sponsored government led by Paolo Gentiloni, who replaced Renzi in December, lacked the political support and a long-enough political runway to complete the needed reforms. "Gentiloni's government is our government", said Agriculture Minister Maurizio Martina.

"I hope that others will do the same, it doesn't hurt", Renzi added, taking a swipe at the rival Five Star Movement, which is running close to the PD in opinion polls but which made a decision to hold its primary contest via an online vote.

The election comes as attention turns to Italy from France where expectations are that Sunday's presidential elections will see centrist Emmanuel Macron beat anti-euro Marine Le Pen, squashing the immediate risk of an anti-Europe party coming to power in the bloc's heartland.

The vote was open to all Italians over 16 years old, European Union citizens residing in Italy and non-EU foreigners with valid residency permits - on condition of paying a donation of at least two euros.

According to the final results released early on Monday, some 2 million people across the country took part in the party internal election, and Renzi won about 73 percent of the votes. The three candidates are former Italian Premier Matteo Renzi, Governor of Apulia region, Michele Emiliano, and Justice Min.

"Rather than a competition, we are facing the legitimisation, a sort of crowning of Renzi as leader of the PD". Minority party dissidents opposing him want to adopt a more leftist stance for the party and criticize Renzi as authoritarian.